The Apollo-type asteroid 1998 KY26 was identified as an
ideal target for the detection of the Yarkovsky effect
(Vokrouhlicky et al. 2000, Icarus 148, 118). At the time of
its 2024 close approach to the Earth, the displacement
arising from the Yarkovsky effect could be as large as 4500
km. However, this 30 meter diameter near-Earth asteroid was
observed for only 12 days in 1998, though there is a radar
detection of it, and it was noted that the orbit
uncertainties could be as large as the expected effect if
the orbit is not carefully monitored. The brightest it will
become prior to the 2024 close approach is V=23.4 in 2013.
At the urging of S. Chesley, a special effort was made to
observe this object during its 2002 opposition, when it
reached only V=24.7, though the three sigma ephemeris
uncertainty was only 16 arcsec. Time was requested and
awarded on the University of Hawaii 2.24-m telescope near
the time of greatest brightness for the object, and the
weather cooperated, though the seeing was slightly worse
than average for Mauna Kea. On each of two nights, nine
separate exposures of 600 sec duration were taken, tracked
at the asteroid's expected rate of motion. Careful
processing and stacking of the nine frames did reveal the
asteroid approximately 13 arcsec from its predicted
location. The improved orbit effectively removes ephemeris
uncertainty as a consideration for future observation
attempts, leaving limiting magnitude as the only serious
consideration. Although it is not yet possible to say
anything about the size of the Yarkovsky effect on this
object, it is possible that optical observations alone may
reveal the effect as early as 2020, provided that continued
astrometric observations are secured in at least 2009 and
2013.

This work was supported by NASA Grant NAG5-4524 to the
University of Hawaii.